The present invention relates to a sampler for collecting drill cuttings, and more particularly to a sampler which collects a theoretically accurate sample of drill cuttings created when blast holes are drilled in open-pit mining operations, e.g. gold or silver mining operations.
In open-pit mineral mining, blast holes are drilled and then partially filled with explosives. The explosives are detonated to turn solid rock into loose rock which can be removed from the pit for further processing in order to extract the mineral of value, e.g. gold and/or silver. The blast holes are conventionally located in a square pattern, or equilateral triangle configuration, and drilled to a uniform depth, e.g., 28 feet. The blast holes are typically half-filled with explosives. Only the top 25 feet of loose rock is removed after blasting to form a 25 foot "bench". A layer of loose rock is left in the pit to ensure that the equipment used to remove the loose rock does not come into contact with solid rock causing excessive wear and tear to the equipment. This process of drilling, blasting and removing loose rock may be repeated a number of times. Open-pit mines are often many "benches" deep.
When blast holes are drilled, samples of the drill cuttings are collected and analyzed in conjunction with samples from other drill holes in the blast hole pattern in order to determine a preferred approach for economically exploiting the mineral of interest.
Drilling is performed using large drilling machines operated by one individual in order to drill a single hole. The drill operator stands on the "deck" of the drill machine which is a platform located above the drill hole. The drill hammer and steel extend down through the drill deck into solid rock such that the cuttings which are removed from the hole during drilling remain below the drill deck. The drill deck is often surrounded by a flexible skirt in order to keep the dust and cuttings which are generated as a result of the drilling away from the operator and below the deck. As the drill hammer and steel are inserted through the drill deck, a dust rubber mounted below the drill deck provides a tight seal against the outer surface of the drill steel preventing cuttings which adhere to the drill steel from being ejected vertically through the deck.
Conventional samplers operate "through-the-deck" or "under the deck". Under the deck samplers require the drill operator to move from the drill deck to the ground in order to insert the sampler under the deck into the sampling environment, or to have a second operator who is responsible for moving the sampler into and out of the sampling environment. A through-the-deck sampler operates more efficiently because a single operator can operate the drill, and get the sampler in and out of the sampling environment, from a location above the deck.
A through-the-deck sampler is inserted into the sampling environment through an opening in the drill deck in order to obtain the sample. One conventional "through-the-deck" sampler utilizes a sample bag which is placed into a stationary tube and then mounted within a sampling rack. The sampling rack fits through an opening in the deck such that when the sampling rack is placed in the sampling environment no drill cuttings or dust can escape up through the opening. An identical sampler is often inserted through a second opening in the deck which is located on the opposite side of the drill in relation to the first opening. This second sampler is added in order to increase the volume of sample collected. The ability of this type of sampler to collect a representative sample during drilling is dramatically effected by changes in drilling equipment (i.e., hammers, air volume, etc.). These types of samplers can collect a sample for analysis, but the integrity of the sample taken can be compromised.
While known samplers are capable of sampling drill cuttings under various conditions, a need remains for a sampler which is capable of obtaining a theoretically accurate sample of blast hole drill cuttings. In addition, the need exists for a through-the-deck sampler which is portable and capable of reducing or preventing contamination of the sample during drilling. The sampler should also be capable of sampling the entire portion of cuttings ejected in its direction, and it should be able to automatically split the sample retrieved in half to provide a smaller, but representative, sample size to reduce handling costs while preserving accuracy. Finally, the need exists for a sampler which is not dependent upon any power source in order to function properly, yet still allows the sampler to close completely in order to prevent sampling during certain periods of drilling.